Download lightning rabbit – an application of sound energy to produce more

APEC Youth Scientist Journal Vol. 3
LIGHTNING RABBIT – AN APPLICATION OF SOUND ENERGY
TO PRODUCE MORE ELECTRICITY
∗
Yu-Ting CHEN1 and Ching-Chung CHANG 1
Taipei First Girls’ High School, Taipei, Taiwan (R.O.C)
1. INTENTION
It is an important environmentally-friendly concept to create and recycle energy. There are
different kinds of energy possibly available on earth. If we make the most of them, we can
reduce the consumption rate of the resources. A feature of piezoelectric materials is to
transfer the mechanical energy into the electric energy. The Japan pavilion in Expo 2010
exhibited a kind of floor made of such a material, which is able to generate electricity if
stepped by passersby. The delivery of sound is based on the change of pressure; therefore, it
is possible theoretically to use sound to generate electricity. (This device has already been
shown in a Disney movie, “Monsters, Inc.”) Learning from some articles and films, I knew
that there has been preliminary development of “sound energy” in recent technology.
Therefore, I think in the near future, using “sound energy” will become an important method
to generate electricity, and I bring up an idea hoping to be applied to daily life in the future.
2. THEORY AND METHOD
In 1880, Jacques Curie and Pierre Curie discovered the piezoelectric effect, which is about
the transfer between mechanical energy and electric energy, and opened the developments
and applications of piezoelectric materials. Scientists have now discovered some
piezoelectric materials such as BaTiO3 and PZT. These materials have been used as ultrasonic
∗
Correspondence to : Yu-Ting CHEN ([email protected])
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vibrator, power floor and power shoes. Besides, scientists are conducting research hoping to
reduce the size of piezoelectric material and develop new materials with more sensitivity.
Recently, the device which can produce electricity by vibration is also developed. As a result,
with the improvement in technique, piezoelectric material and the vibration-powered
generator can become the theories to generate electricity by sound.
3. IDEA
About the design
“Lightning rabbit” is a device, which is an application of sound energy. It is composed of the
sound receivers, sound-generating device, and the battery holder. “Lightning rabbit” can
transfer the sound wave into electric energy and charge the batteries inside to produce energy.
About the structure
This device includes two sound receivers, a sound-generator and a battery holder. The design
of the sound receivers is like the ears of rabbits, which can receive the sound in the
surroundings. Then, they are attached to the sound-generating device and produces electricity
to charge the batteries. They can also be attached to plugs to supply energy for the electric
equipment.
Figure 1. The design of Lightning rabbit
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Front:
Ears ─ receiver, which can detect the volume as well as receive sound
Nose ─ the switch of “Lighting rabbit”
Smile ─ shows how much energy has been stored
Back:
Monitor ─ volume in the surroundings
Battery holder ─ a place to put batteries
4. PRACTICALITY AND FEASIBILITY
Today, people have been able to generate electricity through pressure or vibration. In addition,
there are preliminary results of sound-generation. In my opinion, this device will be produced
with the development of sound-generation techniques. In this way, it is possible to generate
electricity in many places such as schools, factories and streets. This device is portable for
people to charge batteries, and it can also be combined with small electric equipment such as
watches and flashlights, and thus directly supplies electricity for them. Furthermore, this
device can be applied to microphones or necklaces, producing electricity when people are
talking. It can be combined with the collar of the pets producing electricity when the pets
give off sound.
Assume that there is a 750mAh, 1.2V rechargeable battery whose total energy is
750*0.001*1.2*3600=3240 J, and the volume is 60 dB (10-6 W/m2, the appropriate volume
for people). If the transformation percentage of the energy is 100% (not in the real situation),
and if we want to charge the battery within two days, the sound receiver would be 3240/(106
*2*24*60*60)=18750 m2. This area is the same as a 137m*137m square. Apparently, it is
not suitable for recent condition. However, if the volume is 130 dB(the volume when a plane
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takes off), the required area would be 0.002 m2. This area is the same as a 4cm*4cm square
and the feasibility is much higher. Solar energy, which is widely used nowadays, has little
transformation efficiency between light and electricity in primary stage of its development.
However, with the development of semiconductor, the efficiency of solar cells has been
increased dramatically. Therefore, “Lightning rabbit” has large potential and space to develop
in the future.
If we want to operate this device, we can first set them up in places with higher volume, for
example, factories and airports. In addition, to overcome the problem about the insufficient
volume, a possible method is to attach resonance device to the sound receiver. Besides, the
transformation efficiency of the sound-generator also needs to be improved.
5. EXPECTED EFFECTS
“Lightning rabbit” can be used widely, and will become a portable device to receive
vibration of sound in the surroundings and save them as electric power. Besides charging
batteries, it can also be combined with plugs to provide energy for electric equipment. This
design can be set up in public places such as shopping centers, schools and streets, and
therefore reduce the use of electricity in the city. In addition, it is also possible to use the
device to avoid noise. It can switch on once the volume goes beyond a certain volume
threshold to remind people to lower their voice. “Lightning rabbit” can also be designed in
different appearances such as elephants, penguins and mice, and add delight to life.
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6. DESIGN
Figure 2. The demonstration of vibration generator
By attaching PZT to pure copper, and combining each pieces in series, we can measure the
voltage when the device is vibrating. The vibration of sound is too low to be measured.
However, when blowing this generator, the vibration of current can be changed into
electricity and the raise of voltage can be measured.
7. FUTHER WORK
To make the device more sensible, the next step of the experiment is attaching PZT to copper
film. Also, measuring the resonance frequency of different sizes of PZT as well as the voltage
generated by this device is the experiment which can be done in the future.
8. REFERENCES
[1] Vibration-Powered-Generator
http://scimage-tw.blogspot.com/2010/08/vibration-powered-generator.html
2011/5/22
[2] Bullets of Sound on Innovation Nation
http://www.youtube.com/watch?v=veUpc6Y-JtI 2011/5/22
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[3] Environmental Protection Administration Executive Yuan, R.O.C
http://www.epa.gov.tw/ 2011/5/22
[4] http://enjoysci.narl.org.tw/ndl/?p=43&cpage=1g 2011/5/22
[5] http://youku.com/v_show/id_XMjIxODA1NTEy.html 2011/5/22
[6] 中華民國第 49 屆中小學科展 聲音發電
[7] M. S. Majdoub, P. Sharma, and T. Çağin, 2008,
Dramatic enhancement in energy harvesting for a narrow range of dimensions in
piezoelectric nanostructures, APS Phys. Rev. B78, issue12
[8] http://highscope.ch.ntu.edu.tw/wordpress/?p=3331 2011/5/22
[9] http://tw.myblog.yahoo.com/jw!pP7p_fyWBBOSJXonaZUnaQ--/article?mid=2394
2011/5/22
[10] http://www.materialsnet.com.tw/DocView.aspx?id=7361 2011/5/22
[11] http://en.wikipedia.org/wiki/Piezoelectric 2011/5/22
[12] http://en.wikipedia.org/wiki/PZT 2011/5/22
[13] 95 華梵大學機電工程學系專題研究成果報告
壓電式振動微型發電機的設計與製作 胡毓忠、廖偉珈、蔡蕙芹
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